Plant for producing types of tyres different from each other

ABSTRACT

A plant for producing types of tyres different from each other includes a manufacturing unit including a plurality of work stations, devices for transfer and movement of the tyres being produced, and a vulcanizing unit including vulcanizing moulds for the tyres being produced. Each work station is designed to assemble at least one corresponding structural component on at least one type of tyre being produced. The devices for transfer and movement operate between the work stations and provide selective movement for each of the types of tyres being produced in proximity to corresponding work stations. The plant may also include a central processing unit. The central processing unit may control the devices for transfer and movement to coordinate processing stages for each type of tyre in the manufacturing unit and in the vulcanizing unit. Additionally, the plant may include holding stations associated with at least some of the work stations.

The present invention relates to a method for producing tyres which aredifferent from each other within one production plant.

A tyre for vehicle wheels normally comprises a carcass structure,essentially consisting of one or more carcass plies shaped in anessentially toroidal configuration and having their axially opposinglateral edges engaged with corresponding annular reinforcing structuresincorporating circumferentially inextensible inserts usually called“bead wires”. Each annular reinforcing structure is incorporated in whatis known as a “bead” formed along an inner circumferential edge of thetyre for fixing the tyre to a corresponding mounting rim.

A belt structure, comprising one or more strips of belt in the shape ofa closed loop, essentially consisting of textile or metal cords suitablyorientated with respect to each other and with respect to the cordsbelonging to the adjacent carcass plies, is applied to the carcassstructure in a radially external position.

A tread band, normally consisting of a strip of elastomeric material ofsuitable thickness, is also applied to the belt structure in a radiallyexternal position.

It should be noted that, for the purposes of the present description,the term “elastomeric material” denotes the rubber mixture in itsentirety, in other words the whole material formed by at least onepolymer base suitably amalgamated with reinforcing fillers, and/orprocess additives of various types.

A pair of sidewalls, each of which covers a lateral portion of the tyrelying between what is called a shoulder area, located near thecorresponding lateral edge of the tread band, and the correspondingbead, is applied to the opposite sides of the tyre.

Given the above, it should be noted that each type of tyre isessentially distinguished from the others by a set of chemical andphysical, structural, dimensional and appearance characteristics.

The chemical and physical characteristics essentially relate to the typeand composition of the materials, and particularly to the recipes of thevarious mixtures used in the production of the elastomeric materials.The structural characteristics essentially define the number and type ofthe structural components present in the tyre, and their positioningwith respect to each other in the structure of the tyre. The dimensionalcharacteristics relate to the geometrical measurements and to thecross-sectional profile of the tyre (external diameter, maximum chord orwidth, sidewall height and their ratio, in other words the sectionratio) and will be indicated simply as “specification” hereafter. Theappearance characteristics consist of the design on the rolling surfaceof the tread, the ornamental patterns and the various pieces of wordingor distinctive signs reproduced on the tyre, for example on thesidewalls of the tyre, and will be indicated as a whole as “treaddesign” in the remainder of the present description.

The conventional production processes essentially comprise four distinctstages in the manufacture of tyres:

-   a) preparation of the mixtures,-   b) production of the individual structural components,-   c) assembly of the different structural components in succession, to    produce a crude tyre on a drum or other suitable support,-   d) vulcanization of the crude tyre with simultaneous stamping of the    tread design on the external surface of the tyre.

For the purposes of the present invention, “type of tyre” denotes a tyrehaving a given specification, given structural components of which itconsists, and a given tread design.

In an effort to reduce production costs, technological development hasbeen basically orientated towards the search for technical solutionswhich would lead to the production of increasingly fast and reliablemachinery, in such a way as to minimize the time required to produceeach tyre, while maintaining or improving the quality of the finishedproduct.

Thus, plants with high production capacity in terms of pieces producedper unit of time have been produced, using tyre manufacturing machinerywhich has reduced options for modification (or in other words, iscapable of producing only a limited range of types of tyre), but whichmaximize the serial production of tyres having identical structuralcharacteristics. Purely by way of example, in the most up-to-date plantsthe output can be up to approximately two carcasss per minute, and theaverage batch output in one month of operation for each article (type oftyre) can be 3200 pieces, with an article-changeover time of 375minutes.

Attempts have also been made to reduce or eliminate the storage of thesemi-finished products present between one and another of the fourprocess stages listed above, in such a way as to minimize the costs andproblems involved whenever the type of tyre in production has to bechanged. For example, the document EP 922561 proposes a method forcontrolling tyre production, in which, in order to reduce or eliminateboth the crude tyre storage time and the number of crude tyres beingstored, a complex vulcanizing unit is provided, with a number of mouldssuitable for constantly absorbing the output of the complex tyremanufacturing unit. The production of tyres of different types,particularly those having different specifications, is achieved byreplacing and/or adapting from time to time the machinery provided inthe complex tyre manufacturing unit, in conjunction with the replacementof the moulds in the complex vulcanizing unit.

The applicant has found that, in all cases, the production of the tyresentails costs which increase with the variety of types of tyre to beproduced: in particular, it is necessary to intervene in the processesand/or mixture production plants to permit the production of componentswith new and different physical and chemical characteristics and/or inthe production plants of the individual structural components to changethe specification of the tyres being produced. It is also necessary tochange the operating sequence (different assembly method) and/or theequipment and adjustment of the manufacturing machinery whenever achange is made in the structure and/or the specification of the tyre tobe produced. Finally, it is necessary to have at least one vulcanizingmould for each different tread design-specification pair.

All of the above entails continuing costs for the purchase of mouldswith different specifications and different tread designs, and ofdifferent equipment, costs for introducing the latter, losses of outputdue to machine downtime (a change of process or equipment generallycauses machine downtime), and waste of material. For example, in thecase of continuous production of components, machine downtime ofdownstream plants and/or a change in the characteristics of thecomponents generates excess production which has to be rejected, sinceit is impossible to re-use it.

Given these circumstances, in the applicant's opinion the production ofa large number of types of tyre in a single plant is generallyundesirable, particularly if the objective of minimizing costs is to bepursued. In fact, this objective is incompatible with a frequent changeof equipment and production processes. When production processes of theconventional type are used, the applicant has observed that, where thevolume of sales of each individual type is sufficiently high, the numberof the production plants can be multiplied in such a way as to make itpossible to produce a different type continuously in each plant, thusminimizing the aforesaid disadvantages. On the other hand, where thevolumes of sales forecast for specific types are not particularly high,for example on an annual basis, it is also possible in each case tocarry out the whole production for at least one year immediately andcontinuously, to contain the production costs for these types. Thissystem may, however, affect the quality of the sold product, and tendsto increase storage costs, since the products remain in stock for a longperiod. The risk associated with sales also increases, for example as aresult of unforeseen rapid obsolescence of the product, and there is anincrease in the financial costs of capital tied up in the stocks of theproduct and in the installation of the moulds which are to be used onlyfor the restricted period necessary to complete the production of theforecast reduced volume.

In order to tackle these problems, the applicant has already developed aproduction method in which each series of tyres identical to each otheras regards production is broken down into daily lots, each comprising aquantity of tyres sufficient to cover the daily output of one mould. Inthis way the production of tyres having different specifications and/ordifferent constructional characteristics is optimized by eliminating thestorage of large quantities of crude and vulcanized tyres. This methodis described in European patent application EP 875364 in the name of thepresent applicant.

In a tyre production plant, the stage of vulcanization of the tyre iscarried out in a period which is essentially identical for ranges of allthe types of tyres, but on the other hand the tyre manufacturing timediffers considerably according to the type of tyre to be produced.Additionally, the application of even a single component takes differentlengths of time for different types of tyre.

This impedes a frequent change of type within the plant described above,since the creation of waiting times for the vulcanization stage wouldoccur whenever a tyre to be vulcanized belonged to a different type fromthat preceding it in the crude tyre processing sequence.

Moreover, a frequent change of type of tyre within one processing batchalso entails a frequent change of the equipment for making the differenttypes, thus further increasing the waiting times.

For the purposes of the present invention, the term “serial processingplant” denotes a plant in which the individual stages of processing ofthe tyre are carried out in a fixed sequence, in other words in whicheach tyre processing stage starts immediately after the preceding stagehas ended.

The applicant has observed that, in a serial processing plant, the totalproduction process time is dependent on the slowest processing stage.

For the purposes of the present invention, the term “critical processingperiod” denotes a processing period in which no changes are planned inthe equipment during the tyre processing sequence.

The applicant has tackled the problem of controlling the functions ofthe plant in such a way as to produce, within a single critical period,types of tyres which are different from each other, while minimizing thewaiting times which are due primarily to the difference in the rates ofthe vulcanization and crude tyre manufacturing stages between tyres ofdifferent types.

According to the present invention, the applicant has provided a tyreproduction plant in which different types of tyre can be produced withinthe same critical processing period without increasing the waitingtimes.

More particularly, the applicant has found that, in a plant formanufacturing crude tyres of different types by the successive assemblyof elementary components on toroidal drums of predetermined dimensions,it is possible to keep the flow of crude tyres to the vulcanizationstage essentially constant by selecting a pre-set sequence ofintroducing drums corresponding to different types of tyres into theplant, and by alternating the processing of types which require longertimes with the processing of types which require shorter times. Theprocessing sequence of a critical period is determined according to thenumber and types of tyre which are to be produced within the saidcritical period.

Therefore, once the number of tyres to be produced for each type withina critical period has been decided, it is possible to determine asequence for introducing the types of drums into the plant and asequence for the various processing stages which make it possible tokeep the average time for producing the quantity of crude tyres for thiscritical period essentially constant. In a plant of this kind, theprocessing and the sequence of depositing the various components on thedrum are not the same for all the types of tyre, and, at the same time,different types of tyre are produced within the same critical period.

One aspect of the present invention relates to a method for producingtypes of tyres which are different from each other, comprising the stepsof:

-   -   producing a plurality of structural components of tyres in        production;    -   manufacturing types of tyre by assembling these structural        components according to predetermined successive processing        steps, in the proximity of corresponding work stations arranged        in a complex manufacturing unit within which the tyres being        processed are moved by the transfer of the tyres from each work        station to the next;    -   transferring the manufactured tyres to a complex vulcanizing        unit;    -   vulcanizing the tyres in corresponding vulcanizing moulds        associated with the said vulcanizing line,        characterized in that the stage of manufacturing the types of        tyre comprises:    -   providing at least one series of tyres to be produced,        comprising a sequence of tyres consisting of at least a first        and a second type of tyre arranged in a predetermined order,    -   modifying the order of the said series in at least one work        station.

Preferably, the transfer of the tyres from the complex manufacturingunit to the complex vulcanizing unit takes place at a rate equal to therate of transfer of the tyres to each of the said work stations.

In particular, the said series comprises a tyre of the said first typefollowed by at least one tyre of the said second type, such that the sumof the times for the processing of the first type of tyre by the said atleast one work station, in which the tyres of the second type undergothe same processing at least twice, up to the end of the manufacturingof the crude tyre, is shorter than the said rate by a time correspondingto the difference in the processing time required by the said types atthe said at least one work station.

The production of each structural component is carried out in thecomplex manufacturing unit by the processing of at least one basicsemi-finished product, identical for each type of tyre and supplied inpredetermined quantities according to the type of tyre to be produced.

The structural components of each type of tyre are assembled on atoroidal support whose profile essentially reproduces the internalconfiguration of the type of tyre in question.

Preferably, during the manufacturing step each toroidal support issupported and transferred between at least two adjacent work stations bya robotic arm.

In particular, each tyre is transferred into the complex vulcanizingunit together with the corresponding toroidal support.

In particular, at least one of the said structural components isproduced directly on the tyre being processed, during the said assemblystep.

The production of each structural component is preceded by a step ofidentifying the type of tyre being processed which has been transferredto the corresponding work station.

The identification step is implemented by the reading of a codeassociated with a supporting member of the tyre being processed.

Preferably, a plurality of structural components is assembled in atleast one of the said work stations, in corresponding processing units.

Preferably, the said manufacturing line extends along a path in the formof a closed loop, along which the tyres being processed are made toadvance.

A further aspect of the present invention relates to a plant forproducing types of tyre which are different from each other, comprising:

-   -   a complex manufacturing unit having a plurality of work        stations, each designed to assemble at least one corresponding        structural component on at least one type of tyre being        processed;    -   devices for the functional transfer and movement of tyres being        processed, operating between the said work stations;    -   a complex vulcanizing unit having vulcanizing moulds for the        manufactured tyres,        characterized in that the said functional transfer and movement        devices provide the selective movement for each type of tyre        within a work station.

Preferably, the said selective movement comprises the movement of eachtype of tyre between the work stations according to a pre-set sequence.

Preferably, the said functional transfer and movement devices operatebetween the complex manufacturing unit and the complex vulcanizing unitto transfer the manufactured tyres to the latter, at a rate of transferequal to the rate of transfer of the tyres to each of the work stationsarranged along the line of the complex manufacturing unit.

In particular, each of the said work stations comprises:

-   -   feed devices for supplying at least one basic element for        producing the said at least one structural component of the        tyre,    -   application devices for applying the said structural component        to the tyre being processed, this structural component being        produced with the use of the said basic element in a quantity        predetermined according to the type of tyre to be produced.

In particular, each of the said work stations is associated with:

-   -   devices for identifying the type of tyre being processed in the        work station concerned;    -   selection devices for determining the quantity of basic elements        to be used for the production of the structural component of the        tyre being processed.

Preferably, the said identification devices comprise at least one sensorlocated on the complex manufacturing unit and designed to read at leastone code associated with a supporting member of each tyre beingprocessed.

Preferably, the said functional transfer and movement devices operate ontoroidal supports on which the tyres are formed, to sequentiallytransfer each tyre being processed between the work stations arrangedalong the line of the complex manufacturing unit and to the complexvulcanizing unit.

In particular, the said transfer devices comprise at least one roboticarm associated with at least one of the said work stations.

At least one of the said robotic arms comprises pick-up and drivingmembers operating on the said toroidal support to hold it in front ofthe corresponding work station and to make it rotate about one of itsown geometrical axes during the assembly of the said at least onestructural component.

At least one of the said work stations comprises a plurality ofprocessing units, each responsible for the assembly of a correspondingstructural component on each tyre being processed.

A further aspect of the present invention relates to a plant forproducing types of tyre which are different from each other,characterized in that it comprises:

-   -   a complex manufacturing unit having a plurality of work        stations, each designed to assemble at least one corresponding        structural component on at least one type of tyre being        processed,    -   a complex vulcanizing unit, having vulcanizing moulds for the        types of tyre which have been manufactured,    -   devices for the functional transfer and movement of the tyres        being processed, operating between the said work stations and        the complex vulcanizing unit,    -   a central processing unit capable of controlling the said        functional transfer and movement devices in such a way as to        co-ordinate the stages of processing of each type of tyre in the        complex manufacturing unit and in the complex vulcanizing unit.

A further aspect of the present invention relates to a plant forproducing types of tyre which are different from each other,characterized in that it comprises:

-   -   a complex manufacturing unit having a plurality of work        stations, each designed to assemble at least one corresponding        structural component on at least one type of tyre being        processed,    -   a complex vulcanizing unit, having vulcanizing moulds for the        types of tyre which have been manufactured,    -   devices for the functional transfer and movement of the tyres        being processed, operating between the said work stations and        the complex vulcanizing unit,    -   holding stations associated with the said work stations,    -   the number of the said holding stations, of the said moulds, and        of the said functional transfer and movement devices being        selected with respect to each other in order to obtain series        corresponding to the number of tyres of each type to be        produced.

Further characteristics and advantages will be made clear by thefollowing detailed description of the present invention.

FIG. 1 shows a layout of the plant according to the present invention,indicated as a whole by the number 1.

FIG. 2 shows schematically the stages of a tyre production processaccording to the present invention.

The plant 1 comprises a complex manufacturing unit 2 for producing acrude tyre, in which each tyre being processed is manufactured by theassembly of its structural components in a predetermined sequence, and acomplex vulcanizing unit 3 in which each tyre arriving from the complexmanufacturing unit 2 is vulcanized within a corresponding mould 34, 35,36, 37, 38, 39.

The complex manufacturing unit 2 comprises a plurality of work stations5, 6, 7, 8, 9, 10 arranged consecutively along a processing path,preferably of the closed loop type, shown for guidance by the arrows 11in the attached FIG. 1. This line also has a feed station 20, atemperature stabilizing device 21, a first holding station 22, amultiple holding station 23, a second holding station 24, a thirdholding station 25 and a terminal holding station 26.

The work stations 5, 6, 7, 8, 9, 10 are capable of operatingsimultaneously, with each operating on at least one tyre beingprocessed, to assemble at least one of its structural components on tothe tyre.

More particularly, during the assembly stages the various structuralcomponents used in the production of each tyre are conveniently engagedon a supporting member, preferably consisting of a toroidal support ordrum whose profile essentially reproduces the internal configuration ofthe tyre to be produced. This toroidal support is made in such a waythat it can easily be removed from the tyre when the processing has beencompleted.

At least a first and a second type of tyre can be treated simultaneouslyin both the complex manufacturing unit 2 and in the complex vulcanizingunit 3. By way of example, in the following description, with referenceto the layout shown in the attached FIGS. 1 and 2, two different typesof tyre, differing from each other in their dimensional characteristics,are treated simultaneously. Clearly, it is also possible to operatesimultaneously on a different number of types which may have, inaddition or as an alternative to dimensional differences, differences interms of structural components and/or chemical and physicalcharacteristics and/or appearance.

In the layout shown for guidance in the attached figures, the toroidalsupports are shown without distinction between them and the tyres beingprocessed which are engaged on them, and are identified by the letters Aand B, each of which denotes a specific type of tyre.

As may be noted, the tyres being processed are distributed along theline of the complex manufacturing unit 2 in such a way that thedifferent types A and B succeed each other in a pre-set sequence.Additionally, the pre-set sequence of tyres to be produced within acritical period can be divided into a plurality of series having thesame sequence of tyres or having a different sequence, according to thetypes which are to be produced in each series. In the example shown inFIG. 1, a series comprising six tyres, A, B, B, A, B, A, is distributedalong the line of the production plant 1. In this example, a total ofsix toroidal supports, on each of which a corresponding tyre ismanufactured, are therefore operated within the complex manufacturingunit 2.

It should be noted that, for the purposes of the present description,the term “series” denotes a set of tyres of different types or of thesame type, which follow each other in a predetermined sequence. In thecomplex manufacturing unit 2 it is possible to provide, for example, aplurality of series, each consisting of different types of tyre, whichadvantageously succeed each other cyclically, for example according tothe pattern A, B, A, B, or series each of which advantageously consistsof a tyre of a first type interposed between two tyres of a second type,or series each of which consists of tyres which are all of the sametype.

Devices for the functional transfer and movement of the tyres operate inthe plant to sequentially transfer each of the tyres being processed Aand B from one of the work stations 5, 6, 7, 8, 9, 10 of the complexmanufacturing unit 2 to the next, and to the complex vulcanizing unit 3.The said devices also functionally move the toroidal support during thedeposition of at least one of the structural components.

Preferably, these devices comprise one or more robotic arms R1, R2, R3,R4, R5, R6, R7 and R8, each of which is associated with at least one ofthe work stations 5, 6, 7, 8, 9, 10 and is capable of operating on theindividual toroidal supports A or B, to carry out the sequentialtransfer of each tyre being processed.

The tyre is fabricated by moving the toroidal support and orientating itin space and applying the extruded structural components thereon by bothcircumferential and axial deposition.

The said robotic arms advantageously support the said toroidal supportsso that they project, in other words by gripping them at only one sideon the axis of rotation, thus enabling the various components to bedeposited over the whole of the axial extension of the support which hasa curvature with two bends.

A processing unit commands the transfers along the said loop path anddetermines the number and composition of the said series of tyres withina desired critical period. This unit is capable of controlling the saidfunctional transfer and movement devices in such a way as to co-ordinatethe stages of processing on each type of tyre in the complexmanufacturing unit 2 and in the complex vulcanizing unit 3.

More particularly, in the illustrated embodiment there is a firstrobotic arm R1, movable along a guide structure 19 if necessary, andoperating between the complex manufacturing unit 2 and the complexvulcanizing unit 3, to pick up a finished tyre from the latter andtransfer it to the first work station 5, where the tyre is removed fromthe corresponding toroidal support by means of the robotic arm R8. Thetoroidal support A extracted from the tyre is then transferred by thefirst robotic arm R1 from the first work station 5 into the temperaturestabilizing device 21.

If the type to be produced requires the use of a toroidal supportdifferent from that which has been dismantled previously, the roboticarm R1 picks up the appropriate toroidal support from the feed station20 and inserts it into the temperature stabilizing device 21.

This device 21 brings the toroidal support to an adequate temperature topermit the subsequent processing, and particularly to promote theadhesion of the first layer of elastomeric material to the metal of thesupport. This temperature is preferably in the range from 80° C. to 90°C.

A second robotic arm R2 serves to transfer the toroidal support from thetemperature stabilizing device 21 to the second work station 6 where thefirst constructional components of the tyre are assembled. The assemblyoperation may, for example, comprise the coating of the outer surface ofthe toroidal support A with a thin layer of airtight elastomericmaterial, usually called liner, carried out by a liner processing unit61, and the application of any necessary elastomeric strips in the areascorresponding to the beads of the tyre, carried out by strip processingunits 62, and/or the formation of an additional lining layer made fromelastomeric material and laid on top of the liner, carried out by thesub-liner processing unit 63.

Preferably, at the second work station 6, and also at the remaining workstations 7, 8, 9, 10, the formation of each structural component of thetyre is carried out in conjunction with the previously described stageof assembly, by the processing of at least one basic semi-finishedproduct which is identical for each type of tyre A or B and supplied ina predetermined quantity according to the type of tyre to beconstructed.

In particular, at the second work station 6 the production of the liner,the elastomeric strips and/or the additional lining layer canadvantageously be carried out by winding at least one strip-shapedelement made from elastomeric material on to the toroidal support Abeing processed, in consecutively adjacent and if necessary also atleast partially superimposed turns, this element having a width, forexample, in the range from 0.5 to 3 cm, and being drawn directly from acorresponding extruder, from a reel or from other suitable feed devicesassociated with the second work station 6.

The winding of the turns can be advantageously simplified by giving thesecond robotic arm R2 the function of holding the toroidal support A, bymeans of suitable gripping and driving members, and making it rotateabout its own axis, thus moving it suitably in front of pressure rollersor equivalent application devices (not described) combined with feeddevices, in such a way as to produce a correct distribution of the stripwith respect to the outer surface of the toroidal support. For furtherdetails of the procedure for the application of the structuralcomponents on a toroidal support with the aid of a robotic arm,reference should be made to European patent application no. 98830762.5in the name of the present applicant.

When the assembly of the components at the second work station 6 hasbeen completed, the second robotic arm R2 deposits the toroidal support,with the corresponding tyre under construction, at the first holdingstation 22. A third robotic arm R3 picks up the toroidal support fromthe first holding station 22 to transfer it to the third work station 7,where the structural components which contribute to the formation of thecarcass structure of the tyre are assembled.

More particularly, at the third work station 7 one or more carcass pliesare produced and assembled, together with a pair of annular reinforcingstructures in the areas corresponding to the beads of the tyre. In asimilar way to that described with reference to the operating stagescarried out at the second work station 6, each of these structuralcomponents is produced directly at the assembly stage, using a basicsemi-finished product supplied in a predetermined quantity according tothe type of tyre being processed.

For example, the carcass ply or plies can be formed by sequentiallydepositing on the toroidal support a plurality of strip pieces, cutindividually from a continuous strip element formed by a band ofrubberized cords laid parallel to each other. In turn, each annularreinforcing structure can comprise a circumferentially inextensibleinsert consisting, for example, of at least one metal wire element woundin a plurality of radially superimposed turns, together with a fillerinsert of elastomeric material which can be made by applying an elongateelastomeric element wound in a plurality of axially adjacent and/orradially superimposed turns.

Each of the said continuous strip element, metal wire element andelongate elastomeric element, which form the basic semi-finished productto be used in a predetermined quantity to produce the correspondingstructural component, can be taken directly from an extruder, from areel or from other suitable feed devices associated with the third workstation 7.

For further explanations of the procedure for producing the carcassstructure, reference should be made to European Patent Application No.98830472.1 in the name of the present applicant.

In the layout shown in the attached figure, the third work station 7 isdesigned to produce carcass structures such as those described inEuropean Patent Application No. 98830662.7, also in the name of thepresent applicant. The carcass structure described in this patentapplication comprises two carcass plies, each consisting of a first anda second series of strip pieces deposited in an alternating sequence onthe toroidal support. A pair of annular reinforcing structures of thetype described previously is also provided in each bead of the tyre,each of these structures being inserted between the terminal flaps ofthe pieces, belonging to the first and second series respectively, andforming one of the carcass plies, together with an inextensible insertapplied externally with respect to the second carcass ply.

To facilitate the sequential assembly of the various structuralcomponents in the predetermined order, the third work station 7 is madeto be equipped with at least three different work stations designedrespectively for the deposition of the strip pieces (unit 71), of themetal wire element (unit 72), and of the elongate elastomeric element(unit 73), which operate simultaneously, each on a corresponding tyrebeing processed. Consequently, three tyres, even if they are ofdifferent types from each other, can be treated simultaneously in thethird work station 7, each of the tyres being sequentially transferredfrom one to another of the processing units until the carcass structurehas been completed. The sequential transfer of the tyres into thevarious processing units provided at the third station 7 can be carriedout by the third robotic arm R3, assisted if necessary by a fourthrobotic arm R4 and/or by any necessary auxiliary transfer devices and bythe multiple holding station 23, at which more than one toroidal supportcan be present at the same time. This system makes it possible tominimize the waiting periods when the tyre being processed in this workstation are of types which differ from each other; this is because it ispossible to use the multiple holding station 23 to carry out processingon types which require a longer time at the most favourable moment, byadvantageously altering the order of the sequence of arrival of thetoroidal supports at the work station. In the attached FIG. 1, the unit71 for depositing the carcass plies is engaged with a type B tyre andthe unit 72 for depositing the bead wires is engaged with a type A tyre.

On completion of the carcass structure, the fourth robotic arm R4deposits the toroidal support at the second holding station 24.

The fifth robotic arm R5 picks up the toroidal support from the secondholding station 24, to carry it to the fourth work station 8, which inthe illustrated example is occupied by a type A toroidal support. At thefourth work station 8, the structural components serving to form what isknown as the belt structure of the tyre are produced and assembled. Inparticular, a first processing unit 81 provided at the fourth workstation 8 deposits, directly on the previously formed carcass structure,two under-belt strips extending circumferentially in the shoulder areasof the tyre. These under-belt strips can be extruded directly from anextruder and applied with the aid of pressure rollers or equivalentapplication devices. A second processing unit 82 forms a first andsecond belt strip on the carcass structure, each strip being formed bythe sequential deposition of strip pieces laid adjacent to each othercircumferentially, each piece being made by cutting to size a continuousstrip element consisting of a plurality of cords adjacent and parallelto each other and incorporated in an elastomeric layer. A furtherprocessing unit 83 forms a further belt strip winding a continuous cordin turns which are axially adjacent to each other and radiallysuperimposed on the underlying belt layers. Further details of apossible procedure for producing the belt structure are described inEuropean Patent Application No. 97830633.0, in the name of the presentapplicant.

When the belt structure has been completed, the sixth robotic arm R6transfers the tyre being processed to the fifth work station 9. At thefifth work station 9, the toroidal support B is engaged by the roboticarm R6 with the aid of which a tread band is applied, this tread bandbeing produced by the winding of at least one further elastomeric stripelement in consecutively adjacent and superimposed turnings until atread band having the desired configuration and thickness is obtained.In the illustrated example, the operation is carried out by two units 91and 92. When the aforesaid operations have been completed, the sixthrobotic arm R6 deposits the toroidal support at the third holdingstation 25.

The tyre is then transferred to the sixth work station 10, occupied by atype A tyre in the illustrated example. At the sixth work station 10,the toroidal support is engaged by the seventh robotic arm R7 whichcauses it to move suitably in front of corresponding processing units tocarry out the application of abrasion-resistant elements to the areascorresponding to the beads (unit 101), and the application of thesidewalls, which are also produced by winding at least one elastomericstrip in adjacent and/or superimposed turns (unit 102).

When this operation is finished, the seventh robotic arm R7 deposits themanufactured tyre at the terminal holding station 26, before the tyre istransferred to the complex vulcanizing unit 3.

Each of the work stations 5, 6, 7, 8, 9, 10 not only has one or moreprocessing units, but also comprises a feed device for supplying thebasic elements required for the production of the correspondingstructural component, operating in conjunction with application devicespresent in the aforesaid units, which apply the basic element and/or theresulting structural component to the tyre being processed.

The complex vulcanizing unit 3 advantageously comprises at least one setof vulcanizing moulds 34, 35, 36, 37, 38, 39, the number of which isequal to the quantity of tyres included in the said at least one seriesof tyres being processed in the complex manufacturing unit 2. In theillustrated example, six vulcanizing moulds 34, 35, 36, 37, 38, 39 areprovided, each corresponding to the specification of one of the types oftyre manufactured along the line of the complex manufacturing unit 2.

Preferably, the moulds 34, 35, 36, 37, 38, 39 are mounted on a rotatableplatform 30 which can be rotated with a step-by-step movement, in such away that the moulds are made to follow a path, within the complexvulcanizing unit 3, to bring them sequentially, one after the other,next to a loading and discharge station 40 for the tyres beingprocessed. This rotation preferably takes place with a first rotation ina first direction of rotation, followed by a rotation in the directionopposite the first. Alternatively, this rotation may be of the closedloop type.

Each of the moulds 34, 35, 36, 37, 38, 39 is fed with pressurized steamthrough a corresponding connecting line (not shown) extending radiallyfrom a central column in which steam supply devices, consisting of aboiler for example, are integrated or connected in another way. Thewhole rotatable platform 30 can advantageously be enclosed in aninsulated structure having at least one access aperture located next tothe loading and discharge station 40, in order to prevent excessivedissipation of heat to the exterior.

Advantageously, the transfer of the individual tyre being processed intothe corresponding moulds 34, 35, 36, 37, 38, 39 is carried out by therobotic arm R1 at a rate equal to the rate of completion of the crudetyres being processed in the work stations distributed along the line ofthe complex manufacturing unit 2.

The plant described by way of example operates in the following steps,shown schematically in FIG. 2 and associated with the movements of therobotic arms R1, R2, R3, R4, R5, R6, R7 and R8. In the figure, and inthe remainder of the present description, the steps identified by theletter T followed by a progressive number refer to the manufacturing ofa crude tyre, and the steps identified by the letter C followed by aprogressive number refer to the vulcanization of the tyre and to thedismantling of the toroidal support.

-   T1) The robotic arm R1 picks up a toroidal support, termed the    “core” below, from the feed station 20, and inserts it in the    temperature stabilizing device 21.-   T2) The core is extracted from the device 21 by the robotic arm R2    and is positioned in front of an extrusion head of the unit 61. The    arm R2 rotates the core in such a way that the extruder deposits a    strip of elastomeric material on the surface of the core.-   T3) The robotic arm R2 positions the core in front of an extrusion    head of the unit 62. The arm R2 rotates the core in such a way that    the extruder deposits a strip of elastomeric material on the    specified portion of the surface of the core.-   T4) (optional) The robotic arm R2 positions the core in front of an    extrusion head of the unit 63. The arm R2 rotates the core in such a    way that the extruder deposits a strip of elastomeric material close    to the beads of the core.-   T5) The core is deposited by the robotic arm R2 at the first holding    station 22.-   T6) The robotic arm R3 picks up the core from the first holding    station 22 and inserts it into the carcass ply deposition unit 71,    at which a first layer of carcass ply pieces is deposited.-   T7) The robotic arm R3 picks up the core from the carcass ply    deposition unit 71 and inserts it into the bead wire deposition unit    72, within which a pair of annular reinforcing structures is    deposited on the core in the areas corresponding to the beads of the    tyre.-   T8) The robotic arm R3 picks up the core from the bead wire    deposition unit 72 and deposits it in one of the locations of the    multiple holding station 23.-   T9) The robotic arm R4 picks up the core from the holding position    23 and places it in front of an extrusion head of the elastomeric    filler deposition unit 73. The arm R4 rotates the core in such a way    that the extruder applies a strip of elastomeric material on the    beads of the tyre being processed.

The preceding three steps can be repeated a number of times, accordingto the type of tyre which is being produced. For this purpose, themultiple holding station 23, having multiple locations, each capable ofholding one core, is provided, together with two robotic arms R3 and R4for producing the carcass structure.

-   T10) The robotic arm R4 deposits the core at the second holding    position 24.-   T11) The robotic arm R5 picks up the core from the second holding    position 24 and places it in front of an extrusion head of the    under-belt strip deposition unit 81. The arm R5 rotates the core in    such a way that the extruder deposits a strip of elastomeric    material in the shoulder areas of the tyre.-   T12) The robotic arm R5 inserts the core into the belt strip    deposition unit 82.-   T13) The robotic arm R5 picks up the core from the unit 82 and    inserts it into the processing unit 83 which forms a further belt    layer by winding a continuous cord in turns axially adjacent to each    other and radially superimposed on the underlying belt layers.-   T14) The robotic arm R5 deposits the core back in the second holding    position 24.-   T15) The robotic arm R6 picks up the core from the second holding    position 24 and places it in front of an extrusion head of the    under-tread strip deposition unit 91. The arm R6 rotates the core in    such a way that the extruder deposits a strip of elastomeric    material on the crown area of the tyre being processed.-   T16) The robotic arm R6 places the core in front of an extrusion    head of the tread band deposition unit 92. The arm R6 rotates the    core in such a way that the extruder deposits a strip of elastomeric    material on the crown area of the tyre being processed.-   T17) The robotic arm R6 deposits the core at the third holding    station 25.-   T18) The robotic arm R7 picks up the core from the third holding    station 25 and places it in front of an extrusion head of the    abrasion-resistant layer deposition unit 101. The arm R7 rotates the    core in such a way that the extruder deposits a strip of elastomeric    material on the beads of the tyre being processed.-   T19) The robotic arm R7 places the core in front of an extrusion    head of the sidewall deposition unit 102. The arm R7 rotates the    core in such a way that the extruder deposits a strip of elastomeric    material on the sides of the tyre being processed.-   T20) The robotic arm R7 deposits the core at the terminal holding    station 26.

The crude tyre is now complete; the subsequent steps are concerned withthe vulcanization of the tyre and its removal from the core.

-   C1) The robotic arm R1 picks up the core, with the crude tyre    manufactured on it, and transfers it to the complex vulcanizing    unit, and in particular into a vacant vulcanizing mould 39.-   C2) The vulcanizer closes the mould and rotates by one position. The    tyre is vulcanized in the period of one complete rotation of the    vulcanizing apparatus. At the end of each step of this rotation,    each of the other moulds is loaded with a crude tyre to be    vulcanized.-   C3) The first robotic arm R1 picks up the vulcanized tyre, together    with the corresponding toroidal support, from the mould 39, and    deposits it at the first manufacturing station 5, in a station 16    for dismantling the toroidal support.-   C4) The eighth robotic arm R8 removes the toroidal support and    deposits it in a recovery station 28.-   C5) The eighth robotic arm R8 picks up the vulcanized tyre and    deposits it on a storage platform 14 where the tyres produced    previously by the plant can be placed while they are waiting to be    sent to the subsequent finishing and inspection stages.

The procedure for treating the individual tyres along the line of thecomplex manufacturing unit 2 is such that the deposition of a structuralcomponent can advantageously be carried out independently of thecompletion of the production of another component on the immediatelypreceding tyre in the production process. A characteristic of theinvention is that the structural components of the tyre are preparedessentially at the moment of their deposition, thus making it possibleto operate without previously stored semi-finished products, and toadapt each unit immediately to the type of tyre being processed, thusavoiding wastage of material.

Additionally, the operation of each of the processing units located atthe individual work stations 5, 6, 7, 8, 9, 10, and that of each of therobotic arms, is controlled by a programmable local processing unit, insuch a way that the quantity of basic semi-finished products supplied iscontrolled appropriately, together with the movement imparted to thetoroidal support, to ensure that the individual structural components ofthe tyres being processed are correctly formed. In particular, thislocal processing unit can be programmed in such a way as to adapt theoperation of the processing units of the robotic arms to the type oftyre being treated from time to time in each individual work station.

Moreover, in order to impart greater operating flexibility to the plant,without limitation to predetermined sequences of different types oftyre, provision is preferably made to associate each of the workstations 5, 6, 7, 8, 9, 10 with devices for identifying the type of tyrebeing processed, interacting with selection devices to determine thequantity of basic element to be used for producing each structuralcomponent in the work station in question. For example, theseidentification devices can advantageously comprise a reader of bar codesor other types of code associated with the toroidal support of the tyre,which can be identified, by means of suitable reading devices, by thelocal processing unit, for the purpose of selecting the quantity ofsemi-finished product, for example by using pre-set tables of values.

At the moment at which a tyre is transferred to any of the work stations5, 6, 7, 8, 9, 10, the bar code reader identifies the type to which thetyre belongs, enabling the local processing unit to set the operatingprogram of the work station in a suitable way, in addition or as analternative to the instructions received from the central unit.

The movement of the tyres being processed is advantageously managed inthe form of a continuous flow in which the complex manufacturing unit 2is directly connected to the complex vulcanizing unit 3, the sequentialtransfer of the individual tyres being carried out at a rate equal tothe rate of completion of the tyres in the complex manufacturing unit 2,thus advantageously eliminating the need for storing crude tyres instorage buffers provided between the complex manufacturing unit and thecomplex vulcanizing unit.

The possibility of changing the assembly sequence of the variousstructural components according to the type of crude tyre to be producedenables the average manufacturing time to be matched to the vulcanizingtime.

In the preceding description, the production of two different types oftyres, A and B, was covered by way of example. The first type A relatesto a tyre having the 195/65 R15 specification, with what is known as a“single-ply” carcass structure, and the type B relates to a tyre havingthe 215/45 R17 specification, with what is known as a “two-ply” carcassstructure. The type A comprises a single layer of carcass plies, whilethe type B comprises a double layer of carcass plies. Because of thediversity of dimensions and consequently the different volumes of thetwo different types, the processes carried out on type B require alonger time than the processes carried out on type A. However, while theprocesses at the first, second, fourth and fifth work stations arecompatible with the total cycle times, the process at the third workstation 7, at which the carcass structures are produced, issignificantly different for the two types, particularly in that itrequires the repetition of the deposition of a layer of carcass pliesfor type B.

If the processes described above were carried out in succession, itwould then be necessary either to extend the cycle time by adapting themto the type which requires the longer times, or to provide an additionalwork station.

However, the pair of robotic arms R3 and R4 and the multiple holdingstation 23 are able to change the processing sequence.

For example, if the first tyre to arrive at the third work station 7 isa type B tyre, in other words the one requiring a longer processingtime, the pre-set processing sequence is modified. This is made possibleby the fact that some processes require a time shorter than the raterequired to keep the complex vulcanizing unit always supplied with atyre for each rotation of the rotatable platform 30. Thus it is possibleto recover useful time for making the change in the sequence.

The processing time in each processing unit and the rate of transfer aredetermined according to the number of steps of movement required alongthe line of the complex vulcanizing unit 3, in such a way that each tyreA, B can remain in the complex vulcanizing unit for a time at leastsufficient to complete the vulcanization process.

For example, at the carcass structure production station (third workstation) type A requires a minimum processing time of approximately 1.5minutes, and type B requires a minimum processing time of approximately3 minutes, owing to the fact that this type requires a doubleapplication of the carcass plies, as described above.

At the work stations which apply the liner and sub-liner (second workstation), the belt structure (fourth work station), the sidewalls andthe abrasion-resistant strip (sixth work station), the (minimum)processing time is less than 2.5 minutes for both types A and B. Thework station which applies the tread band (fifth work station) requiresa (minimum) processing time of approximately 2.5 minutes for both typesA and B.

The complex vulcanizing unit 3 has six vulcanizing moulds; to carry outvulcanization in the chosen conditions, each mould is required to remainin the vulcanizer for 15 minutes. To achieve this vulcanizing time whilethe rotatable support of the vulcanizer carries out six steps ofrotation, one cover has to be fed to the complex vulcanizing unit onceevery 15:6=2.5 minutes.

According to the data supplied above, this time is compatible with thetimes of the stations 6, 8, 9 and 10, while the third work station 7 iscritical, since type B requires a processing time here which is too longfor the desired rate.

In order to enable the third step to be carried out, a plurality ofseries of types which are initially fed to the complex manufacturingunit is provided.

Each series consist of a number of tyres equal to the number of thevulcanizing moulds.

Each series consists of three type A tyres and three type B tyres,according to a first order, defined as follows: A1 B1 B2 A2 B3 A3 (thenumbers 1, 2, 3 etc. associated with each type A, B in the sequenceidentify the succession in time of the different types of tyre fed inthe sequence).

After the application of the liner and the sub-liner (second workstation) the order in each series remains unaltered.

At the third work station, the processing sequence requires, forexample, the execution of the following consecutive steps:

-   1. production of the single carcass ply on A1; A1 continues to the    following work stations;-   2. production of the first carcass ply on B1; B1 is put to wait in    the multiple holding station 23;-   3. production of the first carcass ply on B2; B2 is put to wait in    the multiple holding station 23 (in a different location from that    occupied by B1);-   4. production of the second carcass ply on B1; B1 continues to the    following work stations;-   5. production of the single carcass ply on A2; A2 continues to the    following work stations;-   6. production of the second carcass ply on B2; B2 continues to the    following work stations;-   7. production of the first carcass ply on B3; B3 is put to wait in    the multiple holding station 23;-   8. production of the single carcass ply on A3; A3 continues to the    following work stations;-   9. production of the second carcass ply on B3; B3 continues to the    following work stations.

After the third work station, the series has a second order, as follows:A1 B1 A2 B2 A3 B3; this second order is different from the initialorder. The number of steps carried out is nine; each step requires aprocessing time of 1.5 minutes, and therefore the total time for whichthe work station is occupied in applying the carcass structure on thesix tyres is 1.5×9=13.5 minutes. The total time is less than 15 minutes,representing the desired rate for the vulcanization of six tyres.

As a result of the pre-set order of the series, together with the stepscarried out at the third work station as described above, the time forthe production of the carcass structure on type B is no longer critical.

In this example, the order is not modified further at the following workstations, and the rate of 2.5 minutes is maintained in all the followingstations, since they all require a processing time which is less than orequal to 2.5 minutes.

Additionally, type A1 is ready for the following station after 1.5minutes, whereas another 4.5 minutes elapse between it and the next typeB1.

In the following processes, type A1 can be slowed by approximately 1minute, while the processing of type B1 has to be accelerated by 1minute. The slowing is carried out by the holding station 23, or byslowing the rate of application of one or more of the subsequentcomponents.

The acceleration of type B1 is achieved by carrying out the followingprocessing in the minimum time, particularly by carrying out theoperations of depositing the belt structure and sidewalls in 2 minuteseach.

The vulcanizing moulds are arranged in accordance with the second order,in other words in the sequence A1 B1 A2 B2 A3 B3, in such a way as toreceive type A where a vulcanizing mould for this type is provided.

The series follow each other along the manufacturing and vulcanizinglines until the end of the critical period, at which point the mouldscan be replaced if different types are to be produced in the followingcritical period.

With the procedure described above, within a critical period of, forexample, eight hours, 96 type A tyres and 96 type B tyres are produced.

In view of the above, for two types, such as A and B, it is necessary tospecify a series in which one type B is followed by at least one type A,such that the sum of the times for the processing of the type A tyres bya predetermined work station (for example that in which B undergoes thesame process at least twice) up to the end of the manufacturing of thecrude tyre is shorter than the average total time of the said processesby a time corresponding to the time difference between the types A and Bin the said predetermined stage.

This makes it possible to carry out the processing step which requiresthe longest time without causing a delay in the execution of thefollowing steps.

A change in the order of the series at the third work station 7 whichforms the carcass structure was described above; the present inventionis also applicable to types of tyres which also differ from each otherin the deposition of other components, for example the belt structures.In this case, the sequence will also be modified at the fourth workstation 8, by providing a further multiple holding station.

More generally, according to the location of the critical stage in theprocessing sequence, the steps will be accelerated or the waiting timesbetween the stages preceding or following the said critical stage willbe reduced, in such a way as to compensate for the excess timeintroduced by the critical step.

Where necessary, a special holding station can be provided.

In the plant according to the present invention, the pre-set series andthe modifications of the order of each series are made possible by thefunctional transfer and movement devices, particularly the robotic arms,which enable the processing steps to be disassociated from each other.This is because a change in the order of the series means that one typeof tyre follows a different processing path from that of another type.The functional transfer and movement devices make it possible, within asingle critical operating period, to use a number of pathssimultaneously, one for each type of tyre being processed.

Each series represents a time package of steps organized in paths, eachof these corresponding to one type of tyre produced. The path throughthe various processing steps determines the type of tyre manufactured.

Additionally, the numbers of the said holding stations, of the saidmoulds, and of the said functional transfer and movement devices canvary according to how many, and which, types of tyre are to be producedwithin a critical period, as well as in relation to the performance ofthe equipment used.

When required, it is also possible to reduce the effective time of thevulcanization process carried out on the individual tyres, for exampleby retarding the injection of the steam into the mould 34, 35, 36, 37,38, 39 after the tyre has been introduced into it. It is thereforepossible, alternatively, to set different effective vulcanization timesfor the various types of tyre being processed.

The present invention also makes it possible to eliminate or at least tominimize the downtimes on each occasion when a type of tyre beingproduced is changed.

This is because, in these cases, the toroidal supports and thevulcanizing mould suitable for the production of one type have to bereplaced with toroidal supports and the vulcanizing mould suitable forthe production of the new type.

This replacement, which, however, is required only when the dimensionaland/or tread pattern characteristics are changed, can be carried outwith minimal effect on output, by providing suitable equipment ifnecessary.

The invention therefore makes it possible to conveniently produce tyresin very small batches, down to a few units, without requiringsignificant increases in the unit cost of the tyres.

1-24. (canceled)
 25. A plant for producing types of tyres different fromeach other, comprising: a manufacturing unit comprising a plurality ofwork stations; devices for transfer and movement of the tyres beingproduced; and a vulcanizing unit comprising vulcanizing moulds for thetyres being produced; wherein each work station is designed to assembleat least one corresponding structural component on at least one type oftyre being produced, wherein the devices for transfer and movementoperate between the work stations, and wherein the devices for transferand movement provide selective movement for each of the types of tyresbeing produced in proximity to corresponding work stations.
 26. Theplant of claim 25, wherein the selective movement comprises the movementof each type of tyre between the work stations according to a presetsequence.
 27. The plant of claim 25, wherein the devices for transferand movement operate to transfer manufactured tyres from themanufacturing unit to the vulcanizing unit at a rate of transfer equalto a rate of moving of the tyres being manufactured to and from thecorresponding work stations arranged in the manufacturing unit.
 28. Theplant of claim 25, wherein each of the work stations comprises: feeddevices for supplying at least one element for making the at least onecorresponding structural component; and application devices for applyingthe at least one corresponding structural component to the tyre beingproduced; wherein the at least one corresponding structural component ismade with the at least one element in a quantity predetermined accordingto the type of tyre being produced.
 29. The plant of claim 28, whereineach of the work stations is associated with: devices for identifyingthe type of tyre being produced; and selection devices for determiningthe quantity of the at least one element.
 30. The plant of claim 29,wherein the devices for identifying comprise at least one sensor of themanufacturing unit designed to read at least one code associated with atoroidal support or toroidal drum of the tyre being produced.
 31. Theplant of claim 25, wherein the devices for transfer and movement operateon a toroidal support or toroidal drum on which the structuralcomponents are assembled to sequentially move tyres being manufacturedto and from the work stations arranged in the manufacturing unit and totransfer manufactured tyres to the vulcanizing unit.
 32. The plant ofclaim 25, wherein the devices for transfer and movement comprise atleast one robotic arm associated with at least one of the work stations.33. The plant of claim 32, wherein the at least one robotic armcomprises pickup and driving members operating on a toroidal support ortoroidal drum to hold the toroidal support or toroidal drum in front ofthe at least one work station and to make the toroidal support ortoroidal drum rotate about a geometrical axis during assembly of the atleast one corresponding structural component.
 34. The plant of claim 25,wherein at least one of the work stations comprises a plurality ofprocessing units, and wherein each processing unit is designed toassemble one or more structural components on the tyres being produced.35. A plant for producing types of tyres different from each other,comprising: a manufacturing unit comprising a plurality of workstations; devices for transfer and movement of the tyres being produced;a vulcanizing unit comprising vulcanizing moulds for the tyres beingproduced; and a central processing unit; wherein each work station isdesigned to assemble at least one corresponding structural component onat least one type of tyre being produced, wherein the devices fortransfer and movement operate between the work stations and between atleast one of the work stations and the vulcanizing unit, and wherein thecentral processing unit controls the devices for transfer and movementto coordinate processing stages for each type of tyre in themanufacturing unit and in the vulcanizing unit.
 36. A plant forproducing types of tyres different from each other, comprising: amanufacturing unit comprising a plurality of work stations; devices fortransfer and movement of the tyres being produced; a vulcanizing unitcomprising vulcanizing moulds for the tyres being produced; and holdingstations associated with at least some of the work stations; whereineach work station is designed to assemble at least one correspondingstructural component on at least one type of tyre being produced,wherein the devices for transfer and movement operate between the workstations and between at least one of the work stations and thevulcanizing unit, and wherein a number of the vulcanizing moulds, thedevices for transfer and movement, and the holding stations are selectedto correspond to a number of each type of tyre to be produced.